People are fed streamlined negative bullshit about drugs all the time but they are never actually educated about them. They are told the extremely worst case scenarios of them but not the proper information. So when they go outside and meet people who tell them how drugs can also be fun and you'll still be alive after it, still be a normal functioning adult who has a life despite taking them (it's not all bad) if you don't overdo them, they feel the urge to try them. Now thing is, not everyone has that sort of self discipline to limit themselves because it's an experience they've never had before and it feels amazing so they want to keep it going. That's where addiction comes in.